fix(package): update d3-scale to version 3.2.0

Closes #16

Author: greenkeeper[bot]

package.json

@@ -37,7 +37,7 @@
         "d3": "^4.12.2",
         "d3-array": "^1.2.1",
         "d3-axis": "^1.0.8",
-        "d3-scale": "^2.0.0",
+        "d3-scale": "^3.2.0",
         "d3-selection": "^1.2.0",
         "d3-shape": "^1.2.0",
         "ion-prism": "^2.0.5",